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Solution: Ampere-meter squared ($\text{A m}^2$ or $\text{J/T}$).

Solution: North, South.

Solution: South, North. (Forming continuous closed loops).

Solution: North-South.

Solution: $-\vec{m} \cdot \vec{B}$ (or $-mB \cos\theta$).

Solution: (b) $\vec{m} \times \vec{B}$

Solution: (a) $0^\circ$ (Minimum potential energy, $U = -mB$).

Solution: (c) Never intersect (Otherwise there would be two directions of magnetic field at the point of intersection).

Solution: (c) Bar magnet (Produces identical exterior magnetic field lines).

Solution: (b) Vector quantity (Directed from South to North pole).

Solution: True (Magnetic length $\approx$ $5/6$ of geometric length because poles reside slightly inside).

Solution: True ($W = \int_{\theta_1}^{\theta_2} mB\sin\theta d\theta$).

Solution:
(P) Torque ($\tau$) $\rightarrow$ (2) $mB\sin\theta$
(Q) Potential Energy ($U$) $\rightarrow$ (3) $-mB\cos\theta$
(R) Magnetic Moment of coil $\rightarrow$ (1) $NIA$

Solution: Zero.

Solution: $0$.

Solution: Monopoles.

Solution: (a) They form continuous closed loops.

Solution: (c) $\oint \vec{B} \cdot d\vec{S} = 0$ (Net flux out of any volume is zero).

Solution: (b) Two smaller, complete dipoles.

Solution: (c) Zero.

Solution: False (It is strictly zero).

Solution: True.

Solution: Declination.

Solution: Dip (or Inclination).

Solution: $0^\circ$ (Zero).

Solution: $90^\circ$.

Solution: $B \cos I$ (where $I$ is angle of dip).

Solution: (a) $B \sin I$

Solution: (b) $B^2 = B_H^2 + B_V^2$ (Pythagoras theorem).

Solution: (c) $45^\circ$ ($\tan I = B_V / B_H = 1$).

Solution: (c) Magnetic poles (Field is purely vertical).

Solution: (a) $10^{-4} \text{ Tesla}$ (1 Gauss).

Solution: False (It varies from place to place).

Solution: False (It points to the magnetic north pole, which is offset from the geographic north).

Solution:
(P) Angle of Dip at Magnetic Equator $\rightarrow$ (2) $0^\circ$
(Q) Angle of Dip at Magnetic Poles $\rightarrow$ (3) $90^\circ$
(R) Ratio of $B_V / B_H$ $\rightarrow$ (1) $\tan I$

Solution: Diamagnetic.

Solution: Ferromagnetic.

Solution: Negative.

Solution: Curie.

Solution: Very large ($\mu_r \gg 1$).

Solution: (c) Copper.

Solution: (b) Iron.

Solution: (c) Small and positive.

Solution: (b) Repelled.

Solution: (c) $\mu_r > 1$ (slightly).

Solution: True (Though it may be masked by stronger paramagnetic or ferromagnetic effects).

Solution: False (It is *inversely* proportional to absolute temperature).

Solution:
(P) Diamagnetic $\rightarrow$ (2) Small negative ($-1 < \chi < 0$)
(Q) Paramagnetic $\rightarrow$ (3) Small positive ($\chi > 0$)
(R) Ferromagnetic $\rightarrow$ (1) Large positive ($\chi \gg 1$)

Solution: Hysteresis.

Solution: Retentivity.

Solution: Coercivity.

Solution: Low (So they demagnetize quickly when current is turned off).

Solution: High (So they are not easily demagnetized by stray fields).

Solution: (c) High permeability, low hysteresis loss.

Solution: (c) Energy dissipated per cycle per unit volume.

Solution: (b) High coercivity (Harder to demagnetize).

Solution: (b) Making transformer cores (To minimize AC heating/energy loss).

Solution: (c) It becomes paramagnetic.

Solution: True (High coercivity means it is difficult to demagnetize).

Solution: True (This is called Hysteresis Loss).